Slew bearing system

ABSTRACT

A method of monitoring wear of a slew bearing system includes steps of assembling a slew bearing system having a first bearing ring and a second bearing ring concentrically positioned relative to each other forming at least upper and lower raceways, a plurality of bearing rollers positioned in each raceway between the first bearing ring and the second bearing ring, and an index system having a first reference connected with the first bearing ring and positioned relative to a second reference on the second bearing ring to provide a measurable distance between the first reference and the second reference, where the measurable distance changes with wear of the slew bearing system; and monitoring a change in the measurable distance between the first reference and the second reference to monitor wear of the slew bearing system.

This application is a divisional application of U.S. patent applicationSer. No. 12/164,345, filed Jun. 30, 2008.

BACKGROUND AND SUMMARY OF THE DISCLOSURE

The present invention is related to bearing systems, and moreparticularly, to slew bearing systems.

Slew bearings are large thrust bearings common to heavy loads. Slewbearings have in the past been used in applications such as steel millsand other heavy machinery. In many instances, the slew bearing is anintegral and critical component of a larger system.

Slew bearings are often installed at the base of equipment to enablerotation of a supported structure. In these installations, it has oftenbeen difficult to access directly the slew bearings for inspection,maintenance, and repair. Accessing the slew bearings often required atleast some disassembly of a larger system, resulting in lostproductivity and higher maintenance costs. Additionally, the difficultyin accessing the slew bearings for inspections increases the likelihoodof unexpected failure. Because slew bearings are large, expensive, andrequire long lead times for replacement, these unexpected failures maysubstantially impact the overall productivity of systems utilizing slewbearings.

A slew bearing system in the past generally included roller bearingspositioned between concentric rings. These prior slew bearing systemstypically relied upon grease as a lubricant. The grease was channeledthrough ports into the slew bearing to lubricate the roller bearings andthe raceways of the bearing rings. In one example, an automatedlubrication system injected grease at regular intervals into the slewbearing.

Prior slew bearing systems employing grease lubrication had severaldrawbacks. When grease was injected into the slew bearing system, excessgrease within the slew bearing was allowed to escape. The exiting greasecollecting around the slew bearing collected dust and created a risk offire especially in high temperature environments such as steel mills.The grease may not adequately reach all of the bearing elements withinthe slew bearing system leading to wear and other damage and prematurefailure of slew bearing systems. Also, grease is generally pressurizedduring injection into the slew bearing, but resides in the bearing underlow pressure and may harden. Hardened grease within the slew bearing hasfurther prevented adequate distribution of lubricant to all of thebearing elements leading to wear and damage in the bearing and prematurefailure of the bearing. In addition, the input ports where the grease isdelivered to the bearing system may become blocked and prevent thegrease from entering the slew bearing.

Furthermore, even when properly lubricated, metal particles may beproduced within slew bearings due to wear between the roller bearingsand the raceways. Slew bearings have also often been employed inoperating environments where external contaminants may enter the slewbearing. Slew bearings even with proper grease lubricant have beendamaged internally by these various forms of contamination. Greaselubricants have tended to hold metal particles and other contaminants,resulting in those contaminants being drawn into contact with thebearing elements within the slew bearing system. Contamination withinthe bearing has led to increased friction diminishing the effectivenessof the slew bearing, as well as mechanical damage such as spalling andbrinneling in the bearing. Grease lubricants have not typically beenfiltered in service and therefore contaminants have tended to collectover time increasing the potential for damage and resulting inadditional failures of slew bearing systems.

Another drawback to grease lubrication has been increased heat withinthe slew bearings. Effective grease lubrication often required fillingthe interstices and internal volume of the slew bearing system. Thegrease typically did not flow through the slew bearing system duringnormal operation. These factors often lead to the slew bearing systemrunning hotter than desired resulting in increased metal fatigue andmore rapid failure of the slew bearing systems.

Grease lubricants have also led to increased clean up costs. The greaseused in prior systems may be delivered to the slew bearing periodicallyresulting in used grease being forced out of the slew bearing system.The used grease tended to build up and maintenance was required toremove the excess grease. This clean up added to maintenance costs.

The grease lubricants used in prior slew bearing systems have also beenexpensive. Many applications required specialized grease to accommodatefor the temperature and operating environment where the slew bearingsystem was employed. Also prior slew bearing systems have not been ableto recycle the used grease resulting in increased operating costs forthe slew bearing system. The disposal of used grease has also beencostly and often required special disposal procedures to comply withenvironmental regulations.

The drawbacks of grease lubrication limited the life expectancy of slewbearing systems. The life expectancy of slew bearing systems hastypically been calculated based upon factors such as the required loadcarrying capability, the effectiveness of grease lubrication, and theoperating temperatures. These problems associated with greaselubrication limited the projected life expectancy of slew bearingsystems, as well as increased the risk of actual failures of the slewbearings. In some applications, replacement of slew bearings has beenrequired at regular intervals, in some cases as frequently as every fewmonths. Given the cost of the slew bearing systems and the difficulty ofinstallation, regular replacement of the slew bearings substantiallyincreased overall operating costs for the slew bearing systems andreduced the productivity of the equipment and systems utilizing slewbearings.

Other prior slew bearing systems have employed oil circulationlubrication. These systems have typically filled the slew bearing withcirculating oil, which may or may not be filtered and recycled. Due tothe size of slew bearings, slew bearings employing oil circulationlubrication have generally required large quantities of oil. In manyinstances, special oils have been required due to the operatingenvironment of the slew bearing resulting in higher material costs. Inany event, special procedures where often required to dispose of theused oil, further increasing the operating costs of these slew bearingsystems. Excess oil within the slew bearing has impeded the movement ofthe roller bearings within the slew bearing system decreasing theeffectiveness of the slew bearing. Another drawback of oil circulationlubrication has been increased heat with the slew bearing. As withgrease lubrication, excess heat within the slew bearing system hasresulted in increased metal wear and metal fatigue, and hastened thefailure of the slew bearing systems.

In light of the drawbacks associated with these prior lubricationtechniques, there continues to be a need for slew bearing lubricationsystems that provide proper lubrication of the bearing elements whileimproving reliability, extending bearing life, and reducing operatingcosts.

A slew bearing system is presently disclosed that comprises a firstbearing ring and a second bearing ring concentrically positionedrelative to each other forming at least upper and lower raceways therebetween, a plurality of bearing rollers positioned in each racewaybetween the first bearing ring and the second bearing ring, a pluralityof delivery nozzles capable of delivering an air and oil mixture intothe raceways adjacent the upper raceway, passages capable of fluidlycommunicating the air and oil mixture through the raceways andcollecting some oil from the mixture adjacent the lower raceway, sealscapable of regulating air flow through the passages and inhibitingoutflow of oil from the raceways, and at least one exit port capable ofoutward flow of air and oil from the raceways adjacent the lowerraceway.

Also disclosed is a slew bearing system that comprises a first bearingring and a second bearing ring concentrically positioned relative toeach other forming at least upper and lower raceways there between, aplurality of bearing rollers positioned in each raceway between thefirst bearing ring and the second bearing ring, a plurality of deliverynozzles capable of delivering an air and oil mixture into the racewaysadjacent the upper raceway, passages capable of fluidly communicatingthe air and oil mixture through the raceways and collecting some oilfrom the mixture adjacent the lower raceway, at least one exit portcapable of outward flow of air and oil from the raceways adjacent thelower raceway, an upper seal positioned between the first bearing ringand the second bearing ring, a lower seal positioned adjacent the firstbearing ring capable of preventing outflow of air and oil from thepassages through the bearing rings, a seal ring positioned adjacent atleast one surface of the second bearing ring, and an air pressurecontrol valve positioned adjacent the seal ring capable of regulatingair flow in the passages.

Also disclosed is a method of detecting wear of a slew bearing systemthat comprises assembling a slew bearing system that comprises a firstbearing ring and a second bearing ring concentrically positionedrelative to each other forming at least upper and lower raceways, aplurality of bearing rollers positioned in each raceway between thefirst bearing ring and the second bearing ring, and an index systemhaving a first reference connected with the first bearing ring andpositioned relative to a second reference on the second bearing ring toprovide a measurable distance between the first reference and the secondreference, where the measurable distance changes with wear of the slewbearing system; and monitoring a change in the measurable distancebetween the first reference and the second reference to monitor wear ofthe slew bearing system.

Also disclosed is an index system having the capability of detectingwear of a slew bearing system comprised of a first bearing ring and asecond bearing ring concentrically positioned relative to each otherforming at least upper and lower raceways, a plurality of bearingrollers positioned in each raceway between the first bearing ring andthe second bearing ring, and a first reference connected with the firstbearing ring and positioned relative to a second reference on the secondbearing ring providing a measurable distance between the first referenceand the second reference, where the measurable distance is capable ofchanging with wear of the slew bearing system.

BRIEF DESCRIPTION OF THE DRAWINGS

Presently contemplated embodiments of the slew bearing system aredescribed below by reference to the following figures:

FIG. 1 is top view of a slew bearing system;

FIG. 2 is sectional view of the slew bearing system of FIG. 1 alongsection line 2;

FIG. 3 is sectional view of the slew bearing system of FIG. 1 alongsection line 3;

FIG. 4 is a detail view of the slew bearing system of FIG. 3;

FIG. 5 is sectional view of the slew bearing system of FIG. 1 alongsection line 5;

FIG. 6 is a detail view of the slew bearing system of FIG. 5;

FIG. 7 is a sectional view of another slew bearing system;

FIG. 8 is a perspective view of a bearing spacer.

FIG. 9 is a detail view of alternative index systems.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring generally to FIGS. 1 through 9, a slew bearing system 10 isdisclosed with air and oil lubrication. The slew bearing system 10 maybe suitable for use in various applications including high temperatureapplications such as steel mills with electrical arc furnaces. As shownin FIG. 1, the slew bearing system may comprise an first bearing ring 20and an second bearing ring 30 concentrically positioned relative to thefirst bearing ring. The first bearing ring 20 and the second bearingring 30 form raceways there between, and a plurality of bearing rollersmay be positioned in each raceway between the first bearing ring and thesecond bearing ring. The bearing rollers are capable of supporting theload carried by the slew bearing. The slew bearing system 10 also has aplurality of delivery nozzles 70, seals, and exits ports 80 arranged asdescribed below.

The first bearing ring 20 and the second bearing ring 30 are generallyfastened to a surrounding system supported by the slew bearing. As shownin FIG. 3 for example, the first bearing ring may be fastened to asupport base 91, while the second bearing ring 30 is fastened to aturret base frame 92. Alternatively, the first bearing ring 20 may befastened to a turret base frame 92, while the second bearing ring isfastened to a support base 91. In any case, the slew bearing system 10may typically enable the turret base frame 92 to rotate relative to thesupport base 91.

The first bearing ring 20 and the second bearing ring 30 may be fastenedto elements of the surrounding system by bolts 93 and nuts 94, as shownin FIG. 3. Alternatively, stud bolts may be used to fasten the bearingrings to the surrounding system. For example, the second bearing ring 30may be fastened to a turret base frame 92 by a stud bolt 93, as shown inFIG. 7. The use of a stud bolt may simplify assembly and installation ofthe slew bearing system 10. In addition, attachment of the first bearingring 20 and the second bearing ring 30 to the surrounding system byother appropriate mechanical devices or techniques are alsocontemplated.

As shown in FIG. 3, the second bearing ring 30 may be formed from twomating pieces, a second bearing ring first portion 31 and a secondbearing ring second portion 32. The cross-section of the second bearingring may be generally U-shaped and positioned around the first bearingring 20. Alternatively, the cross-section of the first bearing ring 20may be generally U-shaped and positioned around the second bearing ring30. The first bearing ring 20 may also be formed from two mating pieces.Other configurations of the first bearing ring and second bearing ringare also contemplated. For example, as shown in FIG. 7, the firstbearing ring 20 and the second bearing ring 30 may have generallyV-shaped grooves with neither the first bearing ring nor the secondbearing ring is positioned around the other.

The configuration of the slew bearing system 10 depicted in FIG. 3 inwhich the second bearing ring is formed of two mating pieces mayfacilitate assembly of the slew bearing system. By way of example, theslew bearing system 10 may generally be assembled by first positioningthe second bearing ring second portion 32. Next, the lower bearingrollers 52 may be positioned, and the first bearing ring 20 placed intoposition concentric of the second bearing ring to contain the lowerbearing rollers. Then the concentric bearing rollers 53 and upperbearing rollers 51 may be positioned, and the second bearing ring firstportion 31 may be placed into position. Alternatively, if the firstbearing ring 20 were formed from two mating pieces, the assembly processmay proceed by first placing a first bearing ring second portion,positioning the lower bearing rollers, placing the second bearing ring,positioning the concentric and upper bearing rollers, and finallyplacing the first bearing ring first portion. Disassembly of the slewbearing system 10 may also be facilitated when the first bearing ring 20or the second bearing ring 30 are formed with two or more mating pieces.

In operation, the slew bearing system 10 may need to be tilted. It maybe desired to identify a tilt axis 12 of the slew bearing. In oneembodiment, a slew bearing system 10 may also comprise an assembly index11 capable of identifying a location along the circumference of thebearing rings. The assembly index 11 may be fastened along thecircumference of the slew bearing at a known position relative to thetilt axis 12. The assembly index 11 may be used to identify the tiltaxis 12 so that the slew bearing system 10 may be properly positionedprior to tilting.

Alternatively, the assembly index 11 may be used to identify a positionalong the circumference of the slew bearing system 10, which should notbe subjected to increased loads often present on a tilt axis. Such aposition may be present due to limitations in the processes used to heattreat large slew bearings. The assembly index 11 may be used to properlyalign the slew bearing system 10 and thereby avoid damaging the slewbearing system.

The second bearing ring 30 may be concentrically positioned relative tothe first bearing ring 20 to form raceways 41 and 42 with the firstbearing ring. The raceways may be channels or grooves between the firstbearing ring 20 and the second bearing ring 30 in which the bearingrollers contact the first bearing ring and second bearing ring to carrythe load of the bearing system. To reduce friction and improve theefficiency of the slew bearing system, the first bearing ring and secondbearing ring may be manufactured to produce a low friction surface forthe raceways. Additionally, the raceways may be hardened to reduce wear.

The configuration of the raceways may depend upon the design of thefirst bearing ring 20 and the second bearing ring 30. As shown in FIG.7, at least an upper raceway 41 and a lower raceway 42 may be formedbetween the first bearing ring 20 and the second bearing ring 30. Inthis example, a plurality of bearing rollers may be positioned obliquelyin the upper and lower raceways between the first bearing ring and thesecond bearing ring to carry the load of the bearing system.Alternatively, as shown in FIG. 3, three raceways may be formedincluding an upper raceway 41, a lower raceway 42, and a concentricraceway 43 to carry the load of the bearing system. Additionally, theslew bearing system may comprise passages capable of fluidlycommunicating air and oil through the raceways and collecting some oiladjacent the lower raceway.

A plurality of bearing rollers are positioned in each raceway betweenthe first bearing ring 20 and the second bearing ring 30 to care theload of the bearing system. Upper bearing rollers 51 may be positionedin the upper raceway 41 and lower bearing rollers 52 may be positionedin the lower raceway 42. Additionally, concentric bearing rollers 53 maybe positioned in the concentric raceway 43, as shown in FIG. 3. Theexpected load on the slew bearing system 10 may determine the number andthe size of the bearing rollers employed. Typically, for greater bearingloads the greater the desired number and size of bearing rollers used.

Various types of bearing rollers may be used in the slew bearing system.By way of example, the bearing rollers may be cylindrical, ball, ortapered bearings. Alternatively, the bearing rollers may be profiled,such that the diameter of a bearing roller is greater in the middle ofthe bearing roller than at the ends of the bearing roller. Bearingrollers with such a profile may prevent stress concentration developingat the ends of the bearing rollers. Alternatively, the bearing rollersmay be spherical bearings or ball bearings when suitable for the load onthe slew bearing system.

The plurality of bearing rollers positioned within each raceway may beseparated by bearing spacers 54. The bearing spacers 54 may prevent thebearing rollers from colliding within the raceways and may ensure thebearing rollers remain distributed throughout the circumference of theslew bearing. Additionally, the bearing spacers 54 may provide passagescapable of fluidly communicating air and oil through the raceways toimprove lubrication of the bearing rollers and raceways. Alternatively,some embodiments of the slew bearing system may employ a full complementof bearing rollers and may not utilize bearing spacers.

As shown in FIG. 8 a, each bearing spacer 54 may be generallyrectangular capable of being positioned around one bearing roller. InFIG. 8 b, the bearing spacer 54 is illustrated positioned around anupper bearing roller 51. Other bearing spacer configurations are alsocontemplated for use with the slew bearing system. For example, abearing spacer may be formed as a strip adapted to position multipleconsecutive bearing rollers. In another example, a bearing spacer may beadapted to be positioned between consecutive bearing rollers.

The bearing spacers 54 may be formed from materials suitable for use ina selected application. For example, the bearing spacers may be formedfrom Delrin® for high temperature applications. Additionally, thebearing spacers may be formed from acetel resin. Alternatively, thebearing spacers may be formed from nylon or other plastic material. Inanother alternative, the bearing spacers may be formed from steel,bronze, or other appropriate metals. The material used to form thebearing spacer may be resistant to high temperatures and may be durableto maintain separation between the bearing rollers when heavy loads areapplied to the slew bearing system.

The distribution of forces in the slew bearing may depend upon theconfiguration of the raceways and bearing rollers. In the three racewayconfiguration shown in FIG. 3, the upper bearing rollers 51 maywithstand downward vertical thrust caused either by downward loads or byoverturning or tipping forces applied to the slew bearing system 10. Theconcentric bearing rollers 53 may absorb radial forces. The lowerbearing rollers 52 may withstand upward vertical thrusts caused byoverturning or tipping forces applied to the slew bearing system 10.Other slew bearing system configurations may distribute these forcesdifferently over two or more sets of bearing rollers positioned in twoor more raceways. For example, in the two raceway configuration shown inFIG. 7, both the upper bearing rollers 51 and the lower bearing rollers52 may withstand both radial and vertical forces applied to the slewbearing system.

In operation, the slew bearing system 10 may enable a turret base frame92 to rotate relative to a support base 91 by enabling the secondbearing ring 30 to rotate relative to the first bearing ring 20. Thebearing rollers and raceways may reduce friction between the firstbearing ring and the second bearing ring, and reduce the force requiredto rotate the slew bearing system 10. Lubrication within the slewbearing system 10 may further reduce friction between the first bearingring and the second bearing ring, and inhibit damage to the bearingrollers and raceways.

In contrast with prior slew bearing systems utilizing greaselubrication, the slew bearing system 10 employs a pressurized air andoil system for lubrication. For example, the pressurized air and oilsystem for lubrication may be the air/oil lubrication system describedin U.S. Pat. No. 6,145,626 to Niemczura, et. al. As shown in FIGS. 3through 6, the slew bearing system 10 also comprises a plurality ofdelivery nozzles 70 and at least one exit port 80. The plurality ofdelivery nozzles 70 may be capable of delivering air and oil into theraceways adjacent the upper raceway, and the exit ports 80 may becapable of outward flow of air and oil from the raceways adjacent thelower raceway. The exit ports 80 may also be capable of maintaining acontrolled amount of oil in the slew bearing system. Additionally, theslew bearing system 10 may comprise seals capable of regulating air flowthrough the passages and inhibiting outflow of oil from the raceways.

The plurality of delivery nozzles 70 may be positioned at multiplelocations. The delivery nozzles 70 may be positioned in the firstbearing ring 20, as shown in FIG. 5. Alternatively, the delivery nozzles70 may be positioned in the second bearing ring 30. As shown in FIG. 6,the delivery nozzles 70 may be positioned to deliver air and oil intothe upper raceway 41. In another alternative, the delivery nozzles 70may be positioned to deliver air and oil to multiple raceways in theslew bearing system. The number of delivery nozzles utilized may dependupon the overall circumference of the slew bearing system 10 and thetotal number of bearing rollers used along with other factors. In oneembodiment, the delivery nozzles may be positioned where grease fittingswere previously used to lubricate a slew bearing system 10. Additionallocations for delivery nozzles 70 may be designed into the first bearingring 20 or second bearing ring 30. Such additional locations may beplugged until needed and may be used as a backup or replacement should adelivery nozzle become damaged.

The exit ports 80 may be capable of outward flow of air and oil from theraceways adjacent the lower raceway of the slew bearing system 10. Theexit ports 80 of the slew bearing system 10 may also be capable ofmaintaining a controlled amount of oil in the slew bearing system. Theexit ports 80 may be positioned at multiple locations in the slewbearing system 10. For example, the exit ports 80 may be positioned inthe first bearing ring 20 or the second bearing ring 30. In anotheralternative, the exit ports 80 may be positioned between the firstbearing ring 20 and the second bearing ring 30. In one embodiment, theslew bearing system 10 may be designed to collect oil in a sump 81 nearthe exit port 80. The sump 81 may be formed as part of the slew bearingsystem between the first bearing ring 20 and the second bearing ring.Alternatively, the sump 81 may be formed between the first bearing ringor the second bearing ring and a sump ring 82 positioned adjacent one ofthe bearing rings. In one example, the sump ring 82 may be generallyL-shaped in cross section, as shown in FIG. 5. In any case, the sumpring 82 may be formed as a single piece or may be formed from one ormore mating pieces. The sump 81 may also be capable of maintaining adesired amount of oil within the slew bearing system. In anotherembodiment, oil may be maintained in an external sump, oil reservoir, orsimilar external collecting device rather than inside the slew bearingsystem.

Additionally, the exit ports 80 may be adjusted to regulate the amountof oil that will be maintained in the slew bearing system 10. Forexample, as shown in FIG. 3, the exit port 80 may be a stand pipeadjusted upward in length to maintain more oil in the slew bearingsystem, or may be adjusted downward in length to maintain less oil inthe slew bearing system. The exit ports 80 may also be removable fromthe slew bearing system to enable oil to be drained from within the slewbearing system. The slew bearing system 10 may also comprise drain plugs83 capable of outflow of oil from the passages of the slew bearingsystem. The drain plugs 83 may be removed to drain oil from the slewbearing system 10. Additionally, the drain plugs 83 may be capable ofmagnetically capturing metal particles from the oil. A magnetic drainplug may improve the reliability of the slew bearing system 10 byassisting in removal of contaminants from the slew bearing system thatcould damage the bearing rollers and raceways. In one example, the exitports 80 and the drain plugs 83 may be positioned in the sump ring 82,as shown in FIG. 4.

In another embodiment, the slew bearing system 10 may comprise two exitports 80 positioned adjacent the tilt axis 12 of the slew bearingsystem. When the slew bearing system 10 is tilted during operation, oilmay flow within the slew bearing system to the lowest point. Bypositioning exit ports 80 adjacent the tilt axis 12 of the slew bearingsystem 10, the oil level at the exit port may be maintained when theslew bearing system 10 is tilted, and the possibility of oil exiting theslew bearing system 10 when the slew bearing system is tilted may alsobe reduced.

The slew bearing system 10 also has seals capable of regulating air flowthrough the passages and inhibiting outflow of oil from the raceways. Asshown in FIG. 5, the slew bearing has an upper seal 61 positionedbetween the first bearing ring 20 and the second bearing ring.Additionally, the slew bearing system 10 may have an upper seal cover 65positioned to assist in positioning the upper seal 61. The upper sealcover may increase the pressure on the upper seal to help regulate airpressure within the slew bearing system. As shown in FIG. 6, the upperseal cover 65 may be fastened to the first bearing ring. The upper sealcover may extend over a least a portion of the upper seal.Alternatively, the upper seal cover 65 may be fastened to the secondbearing ring. In another alternative, the upper seal cover may also befastened to the upper seal.

The slew bearing system 10 may also comprise a lower seal 84 positionedadjacent the first bearing ring 20 capable of preventing outflow of airand oil from the passages through the bearing rings. Alternatively, thelower seal 84 may be positioned adjacent the lower raceway. The lowerseal may also be positioned between the first bearing ring 20 and aportion of the sump ring 82 to inhibit oil from leaking out of the sump.As shown in FIG. 3, the lower seal may be formed as an O-ring or similargasket capable of preventing outflow of air and oil. As with the upperseal, a lower seal cover, not shown, may also be employed capable ofapplying a force to assist in positioning the lower seal.

The slew bearing system 10 may also comprise an air pressure controlvalve 62 positioned between the second bearing ring and the firstbearing ring. Additionally, the slew bearing system 10 may also comprisea seal ring 63 positioned adjacent the second bearing ring. In anotheralternative, the air pressure control valve 62 may be positionedadjacent the seal ring 63, as shown in FIG. 3. The air pressure controlvalve 62 may be capable of regulating the air flow through the passagesand raceways of the slew bearing system. For example, the air pressurecontrol valve 62 may not separate from the seal ring during normaloperation, but may operate as a relief valve when the air pressurewithin the slew bearing system increases.

The seal ring 63 may be positioned adjacent the second bearing ring witha predetermined gap there between. To facilitate installation andalignment of the seal ring 63, the seal ring may be designed with a sealring index 64 to ensure the proper positioning of the seal ring relativeto the second bearing ring. The predetermined gap between the seal ring63 and the second bearing ring may be sized so that the air pressurecontrol valve 62 fits securely between the seal ring and the secondbearing ring. In one embodiment, the air pressure control valve 62 maybe inserted into an aperture in the second bearing ring second portion32, as shown in FIG. 4. The seal ring 63 may then be installed so thatthe seal ring 63 in combination with the air pressure control valve 62may regulate the air pressure within the slew bearing system. In anotherembodiment, the air pressure control valve may be inserted into anaperture in the seal ring such that when the seal ring is installed theair pressure control valve operates in combination with a surface of thesecond bearing ring.

Also as shown in FIG. 4, the slew bearing system 10 may comprise an airpressure control valve cover 66. The air pressure control valve cover 66may be positioned adjacent at least one surface of the second bearingring and covering at least a portion of the air pressure control valve62. As shown in FIG. 4, the air pressure control valve cover 66 may befastened to the seal ring 63 adjacent to the second bearing ring secondportion 32 and may also extend over at least a portion of the airpressure control valve 62. To reduce friction during operation of theslew bearing, it may be desired to maintain a gap between the airpressure control valve cover 66 and the second bearing ring.Alternatively, the air pressure control valve cover 66 may be fastenedto the second bearing ring, and a gap maintained between the airpressure control valve and the seal ring. In another alternative, theair pressure control valve cover 66 may be fastened to the air pressurecontrol valve 62 and may apply a force to assist in positioning the airpressure control valve.

Over time the seals may wear and need to be replaced. To facilitatereplacement, it may be desired for the seals to be separate components.Alternatively, the seals may be an integral part of the first bearingring 20, the second bearing ring 30, or the sump ring 82. Variousmaterials may be used to form the seals. For example, the seals may beformed from industrial grade polymer material appropriate for use in ahigh temperature environment. The seal covers may protect the seals fromthe external environment to reduce the risk of the seals being damaged.

By way of example, the air pressure within the raceways of the slewbearing system 10 may be maintained in the range between 2 and 5 psig.Pressurized air may enter the slew bearing system through the deliverynozzle and the seals and the air pressure control valve may maintain theair pressure within the slew bearing system. The upper seal 61 may bedesigned to withstand greater pressure than the lower seal 84 and theair pressure control valve 62 so that if a leak should develop thepressurized air and oil may still flow from the upper raceway downthrough the other raceways to enable continued lubrication of theraceways and bearing rollers.

During operation, pressurized air and oil may be combined. In oneembodiment, a measured intermittent delivery of oil may be made into acontinuous flow of pressurized air. The amount of oil delivered into theflow of pressured air may be less than the amount of lubricant requiredwith prior systems. The oil and air may be combined through the use of amixing block, mixing tee, or other similar components known in the priorart. The pressurized air and oil may then pass through hoses or pipes tothe delivery nozzles 70 and be delivered into the raceways of the slewbearing system 10. The pressurized air and oil carries lubricating oilto the raceways and the bearing rollers positioned therein. Thepressured air may be increased within the slew bearing system 10 and theincreased air pressure within the slew bearing system may be regulatedby the seals as previously discussed. This increased air pressure withinthe slew bearing system 10 may reduce the likelihood of contaminantsentering from the surrounding environment into the slew bearing system.Also, the increased air pressure within the slew bearing system 10 mayforce the oil lubricant into the raceways improving the effectiveness ofthe lubrication between the raceways and bearing elements. By reducingcontamination and improving the lubrication, the slew bearing system 10is less likely to be damaged or wear and the reliability and operatinglife may be increased.

The oil exiting the slew bearing system 10 through the exit ports 80 iscollected for reuse or disposal. The slew bearing system may alsocomprise hoses or pipes connected to the exit ports 80 to channel theused oil to a storage container. The used oil may then be discarded orfiltered to remove contaminants and reused. The filtered oil may then beredelivered into the slew bearing system 10 through the delivery nozzles70 as described above. In one embodiment, the pressurized air and oilmay be delivered into the slew bearing near the upper raceway 41, asshown in FIGS. 5 and 6. The oil may then be drawn through the concentricraceway 43 and the lower raceway 42 by gravity and pressure drop untilthe oil reaches the exit port 80. The oil may continuously flow throughthe raceways by the pressurized air within the slew bearing system. Theslew bearing system 10 may be designed to collect oil in the sump 81near the exit port 80. Alternatively, an oil reservoir or similarcontainer may be provided outside of the slew bearing system 10 tocollect used oil.

Also disclosed is an index system having the capability of monitoringwear of a slew bearing system. The index system is a first bearing ringand a second bearing ring, a first reference connected with the firstbearing ring and positioned relative to a second reference on the secondbearing ring providing a measurable distance between the first referenceand the second reference. The measurable distance is capable of changingwith wear of the slew bearing system. With use, the raceways, bearingrollers, and other components of the slew bearing system 10 wearresulting in the position of the second bearing ring changing relativeto the first bearing ring. As the position of the second bearing ringchanges, the measurable distance between the first reference and thesecond reference changes indicating wear of the slew bearing system. Achange in the measurable distance may also indicate a need formaintenance or inspection prior to actual failure of the slew bearing.The index system provides a method of monitoring wear of a slew bearingsystem by monitoring change in the measurable distance between the firstreference and the second reference.

As shown in FIG. 4, the first reference may be an air pressure controlvalve cover 66 positioned adjacent at least one surface of the secondbearing ring. The second reference may be a notch 67 formed in the outersurface of the second bearing ring as shown. As illustrated in FIG. 4,the notch 67 is formed in the outer surface of the second bearing ringsecond portion 32. In this configuration, the air pressure control valvecover 66 extends into the notch 67, but may not contact the secondbearing ring but may form a gap between the air pressure control valvecover 66 and at least one surface of the second bearing ring. The gap isa measurable distance capable of changing with wear of the slew bearingsystem. In one embodiment, the gap may be approximately 0.030 inches(7.62 millimeters) and may be measurable, for example, with a feeler orclearance gauge capable of small measurements, e.g., down to 0.001inches. In another embodiment, the measurable distance between the firstreference and the second reference may be monitored by an automatedsystem capable of providing an alarm when the change in the measurabledistance exceeds a threshold.

Referring generally to FIG. 9, other configurations of the firstreference and the second reference are also contemplated for use withthe present disclosure. For example, as shown in FIG. 9A, the firstreference may comprise an air pressure control valve cover 66 and thesecond reference may comprise a reference mark 68 formed on or in thesurface of the second bearing ring. In other alternatives, the firstreference may comprise a projection or a seal cover attached to thefirst bearing ring. As shown in FIG. 9B, the first reference maycomprise the seal ring 63 while the second reference comprises aprojection 69 from the second bearing ring. The projection from thesecond bearing ring may be a seal cover, an air pressure control valvecover, or another protrusion forming a measurable distance with thefirst reference. In yet another alternative, the first reference maycomprise a notch 71 attached to the first bearing ring. A projection 69from the second bearing ring may extend into the notch 71 attached tothe first bearing ring to form the measurable distance. In yet anotheralternative, the first reference may comprise the upper seal cover 65,and the second reference may comprise a notch formed on a surface of thesecond bearing ring first portion 31, as shown in FIG. 6.

In any case, the location of the first reference and the secondreference should be selected so that the measurable distance may bereasonably accessible for monitoring and inspection. In eachalternative, the measurable distance may change with wear of the slewbearing system, and the change in the measurable distance between thefirst reference and the second reference may allow monitoring of thewear of the slew bearing system.

The slew bearing system 10 employing pressurized air and oil lubricationhas several advantages over oil circulation and grease systems. Theamount of oil used is reduced, thereby reducing cost and the risk offire. Non-flammable oils may be utilized to further reduce the firerisks, but with increased costs. Unlike grease which may only be usedonce, the oil may be filtered and reused multiple times. Also, thevolume of oil used to lubricate a slew bearing system 10 employingpressurized air and oil lubrication may be less than the volume of oilused for circulating oil lubrication, yet be more effective inlubricating the bearing system since oil circulation systems may bedeficient in delivering oil to parts of the bearing system at times. Byusing less oil, leakage of oil from the bearing may also be reduced. Theability to reuse the lubricant and use less oil reduces the total amountof lubricant reducing the operating cost of the system. Also, by reusingthe oil, the cost of disposing of used lubricant in compliance withenvironmental regulations may be reduced. The specific lubricantidentified as an air-oil mixture need not be an oil or classified as anoil. The air-oil mixture may be formed from any suitable lubricantcapable of being mixed with air or other suitable gas.

The pressurized air may flow continuously through the slew bearingsystem 10 and oil may be injected only at irregular intervals asrequired to lubricate the raceways and bearing rollers. In oneembodiment, oil may be injected on regular intervals, such asapproximately every thirty minutes. In any event, oil generally isdelivered more or less frequently depending upon the lubricationrequirements of the slew bearing system. The flow, pressure, and volumeof the air and oil may also be monitored to provide diagnosticinformation on the operation and wear of the slew bearing system.Potential failure of the lubrication system may be detected earlier, andtherefore maintenance may be performed before the slew bearing system isdamaged. The slew bearing system also may operate at a lower temperatureas a result. Unlike grease and oil circulation systems, air-oillubrication does not fill the entire volume of the slew bearing systemand therefore friction within the system is reduced. Additionally, thecontinual flow of air within the slew bearing system may provide coolingto the system. The temperature of the air and oil may also be measuredto detect elevated temperatures within the slew bearing system, andassist in monitoring the operation and performance of the bearingsystem.

The system may filter the air and oil to remove contaminants andparticulate matter created within the slew bearing system. Unlike greaselubricants which retain contaminants, the filtered air and oil may beless likely to collect foreign matter that could damage the raceways andbearing rollers. Further, the oil may be completely flushed from theslew bearing system allowing for analysis of any containments to assessthe extent of wear within the slew bearing system. By removingcontamination from the slew bearing system and improving the ability toinspect the slew bearing, the pressurized air and oil lubrication mayenhance the reliability of the slew bearing system and reduce thefrequency of unexpected failures.

While the invention has been described with detailed reference to one ormore embodiments, the disclosure is to be considered as illustrative andnot restrictive. Modifications and alterations will occur to thoseskilled in the art upon a reading and understanding of thisspecification. It is intended to include all such modifications andalterations in so far as they come within the scope of the claims, orthe equivalents thereof.

What is claimed is:
 1. A method of monitoring wear of a slew bearingsystem comprising: (a) assembling a slew bearing system comprising: afirst bearing ring and a second bearing ring concentrically positionedrelative to each other forming at least upper and lower raceways, aplurality of bearing rollers positioned in each raceway between thefirst bearing ring and the second bearing ring, and an index systemhaving a first reference connected with the first bearing ring andpositioned relative to a second reference on the second bearing ring toprovide a measurable distance between the first reference and the secondreference, where the measurable distance changes with wear of the slewbearing system, wherein the second reference is formed in, formed on, orprojects from an outer surface of the second bearing ring such that thelocation of the measureable distance for monitoring wear is accessiblefrom outside the first bearing ring and the second bearing ring; and (b)monitoring a change in the measurable distance between the firstreference and the second reference to monitor wear of the slew bearingsystem.
 2. The method of monitoring wear of a slew bearing system ofclaim 1 where the second reference comprises a notch formed in the outersurface of the second bearing ring.
 3. The method of monitoring wear ofa slew bearing system of claim 1 where the second reference comprises aprojection from the second bearing ring.
 4. The method of monitoringwear of a slew bearing system of claim 1 where the second referencecomprises a reference mark formed on the surface of the second bearingring.
 5. The method of monitoring wear of a slew bearing system of claim1 where the first reference comprises an air pressure control valvecover positioned adjacent at least one surface of the second bearingring.
 6. The method of monitoring wear of a slew bearing system of claim1, the step of monitoring a change in the measurable distance comprisingusing a spark plug gap gauge to measure the measurable distance betweenthe first reference and the second reference.
 7. A slew bearing systemwith an index system having the capability of monitoring wear of theslew bearing system comprising: (a) a first bearing ring and a secondbearing ring concentrically positioned relative to each other forming atleast upper and lower raceways, (b) a plurality of bearing rollerspositioned in each raceway between the first bearing ring and the secondbearing ring, and (c) a first reference connected with the first bearingring and positioned relative to a second reference on the second bearingring providing a measurable distance between the first reference and thesecond reference, where the measurable distance is capable of changingwith wear of the slew bearing system, wherein the second reference isformed in, formed on, or projects from the second bearing ring such thatthe location of the measurable distance for monitoring wear isaccessible from outside the first bearing ring and the second bearingring.
 8. The slew bearing system of claim 7 where the first referencecomprises a projection attached to the first bearing ring.
 9. The slewbearing system of claim 7 where the first reference comprises a sealcover attached to the first bearing ring.
 10. The slew bearing system ofclaim 7 where the first reference comprises an air pressure controlvalve cover positioned adjacent at least one surface of the secondbearing ring.
 11. The slew bearing system of claim 7 where the firstreference comprises a notch attached to the first bearing ring.
 12. Theslew bearing system of claim 7 where the second reference comprises anotch formed in the outer surface of the second bearing ring.
 13. Theslew bearing system of claim 7 where the second reference comprises aprojection from the second bearing ring.
 14. The slew bearing system ofclaim 7 where the second reference comprises a reference mark formed onthe surface of the second bearing ring.
 15. A method of monitoring wearof a slew bearing system, comprising: monitoring a change in themeasurable distance between a first reference related to a first bearingring and a second reference related to a second bearing ring to monitorwear of the slew bearing system; wherein the first reference is formedin, formed on, or projects from an outer surface of the second bearingring; wherein the second reference is formed in, formed on, or projectsfrom an outer surface of the second bearing ring; and wherein themeasureable distance for monitoring wear is accessible from outside thefirst bearing ring and the second bearing ring.
 16. The method of claim15, wherein the first reference or the second reference is a referencemark, a notch, or a projection.
 17. The method of claim 15, wherein thefirst reference or the second reference is a seal cover, air pressurecontrol valve cover, or seal ring.
 18. An index system for a slewbearing system, comprising: a first reference formed in, formed on, orprojecting from a first bearing ring; a second reference formed in,formed on, or projecting from a second bearing ring; wherein ameasureable distance is created between the first reference and thesecond reference for monitoring wear; and wherein the measureabledistance is accessible from outside of the first bearing ring and thesecond bearing ring.
 19. The index system of claim 18, wherein the firstreference or the second reference is a reference mark, a notch, or aprojection.
 20. The index system of claim 18, wherein the firstreference or the second reference is a seal cover, air pressure controlvalve cover, or seal ring.